1. Field of the Invention
The present invention relates to an anode provided with an active material layer containing silicon (Si) as an element, a method of manufacturing the anode, and a battery including the anode. In particular, the invention relates to an anode suitable for forming an active material layer by vapor-phase deposition method, a method of manufacturing it, and a battery including it.
2. Description of the Related Art
In recent years, as mobile devices have been sophisticated and multi-functionalized, a higher capacity of secondary batteries as a power source for these mobile devices has been demanded. As a secondary battery to meet such a demand, there is a lithium ion secondary battery. However, since graphite is used for the anode in the lithium ion secondary battery in practical use currently, the battery capacity thereof is in a saturated state and thus it is difficult to attain a vastly high capacity thereof. Therefore, it is considered to use silicon or the like for the anode. Recently, forming an active material layer on a current collector by vapor-phase deposition method or the like has been reported. Silicon or the like is largely expanded and shrunk due to charge and discharge, and thus there has been a disadvantage that the cycle characteristics are lowered due to pulverization. However, when using the vapor-phase deposition method or the like, such pulverization can be prevented, and the current collector and the active material layer can be integrated. In the result, electron conductivity in the anode becomes extremely favorable, and high performance both in the capacity and the cycle life is expected.
In general, in a battery, electrons generated by electrochemical reaction in the battery need to be taken out outside via a current collector and a lead. In the past, to improve weldability, an exposed portion on which an active material layer is not provided is left in part of a current collector. An anode lead is attached to the exposed portion by ultrasonic welding or the like. For forming an active material layer of an anode by vapor-phase deposition method, for example, forming the active material layer on the current collector in a given pattern by using a shutter, a mask or the like has been proposed (for example, refer to Japanese Unexamined Patent Application Publication No. 2003-162999).